1. Field of the Invention
The present invention relates to methods and apparatus for accessing the thoracic duct and the right lymphatic duct without general surgery for the purpose of collecting lymphatic white cells.
2. Discussion of the Prior Art
The majority of immune response physiology in humans is developed through white cells residing primarily in circulating blood, synovial fluid and lymph. In recognition of this fact, methods of extracting, treating and readministering these white cells, in particular T-cells, is continually gaining acceptance as a potentially effective modality for treating cancer, infections and autoimmune diseases. The current white cell extraction method of choice is leukopheresis of blood, in which a concentrated white cell solution is separated and extracted from whole blood.
While leukopheresis of blood has been an effective means of accessing and collecting white cells from blood, only about 7% of all white cells reside in blood at any one time. The wealth of circulating white cells contained in lymph fluid and in lymph nodes cannot be accessed by this method. Further, the majority of all circulating T-cells are found in lymph fluid and, therefore, cannot be accessed directly by leukopheresis of blood. The aforementioned drawbacks of present techniques for accessing white cells have limited the scope and efficacy of many white cell therapies.
Past efforts to access lymph fluid have involved general surgical procedures to cannulate the thoracic duct which transports approximately two-thirds of all lymph fluid into the bloodstream. In this procedure, the thoracic cavity is opened, the thoracic duct is severed from its junction with the left subclavian and internal jugular veins, and a cannula is sutured into the severed duct. Severe problems have developed in the majority of patients undergoing this procedure. Persistent cannulae-associated infections have developed which have required antibiotic therapy to control. In many cases, the thoracic duct has ruptured causing lymph fluid to leak into the thoracic cavity, requiring frequent lavage and drainage to control. Thoracic duct lymph leakage has also caused a general reduction in circulating T-cells and B-cells, which has resulted in symptoms of immune suppression. Also, frequent fibrin sheath formation around the tip of the cannulae has caused flow restriction and in some cases blockage of the cannulae. For these reasons, thoracic duct cannulation using general surgery has not been particularly acceptable to the medical community.
What has been urgently needed is an efficient method of accessing lymph fluid to obtain large quantities of white cells for white blood cell treatments, and one which avoids the high cost and severe complications associated with the thoracic surgery. Recent improvements in biomaterials have made it possible to conduct a central venous catheterization procedure to access the thoracic and right lymphatic ducts. This methodology together with the apparatus for accomplishing it forms the subject of the present invention.